Punch press and method of operation



Oct. 29, 1957 E. J. VOSLER E AL 2,811,057

PUNCH PRESS AND METHOD OF OPERATION Filed Oct. 14. 195 3 United States Patent PUNCH PRESS AND METHOD OF OPERATION Edward J. Voslerand Rodger F. Marsh, Dayton, Ohio, assignors to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application October 14, 1953, Serial No. 386,097 1 Claim. (Cl. 7839) This invention relates to presses and is particularly concerned with presses of the crank type.

Specifically, the invention is directed to means for use in combination with the crank type press wherein dead center conditions may be easily remedied so that the press can be quickly placed in operation without the necessity of complete dismantlement.

In crank type presses, a dead center condition frequently occurs when the press is in use. This condition arises from the fact that the crank reaches the end of its stroke at a point wherein the punch and die members of the press are in bottomed condition whereby the punch reaches the limit of movement at the time the crank is at the limit of its movement. This generally freezes the press and requires dismantlement of the press in order to relieve the pressure so that the crank can be turned.

This invention is directed to a means for curing this difiiculty wherein a spacer plate is used in conjunction with the die or punch member. This spacer plate comprises a sandwich of two plates of steel, for example, disposed on either side of the spacer member of a low melting point metal coextensively bonded or otherwise suitably secured to the two sheets of steel. This spacer is then positioned between the press platen and the die and when the press becomes jammed, due to a dead center condition, it is simply necessary to melt the low melting point spacer metal to relieve the condition whereupon a new spacer may be placed in position and the old spacer may be reassembled with new low melting point metal.

It is, therefore, a still further object of the invention to provide a heat destructible spacer for use in combination with a punch press, which spacer may be readily at least partially destroyed by heat to relieve pressure within the press.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing wherein a preferred embodiment of the present invention is clearly shown.

In the drawing:

Fig. 1 shows a diagrammatic view of a crank type press in perspective.

Fig. 2 shows a view through the heat destructible sandwich or spacer member.

Fig. 3 shows a modification of the invention wherein electrical heating elements are maintained within the steel supporting plate.

Fig. 4 shows a modification of the invention wherein the tubes are cast within the heat destructible member.

Referring specifically to the drawing, illustrates a punch press having a frame member 22, a movable platen 24 attached by means of a link 26 to a crank member 28 which is driven by suitable means, for example, a large pulley 30 which is attached to power means, not shown. The platen 24 carries a punch or die member 32 which cooperates with a die member 34 supported in the bed plate or platen 36. Platen 24 may be guided for movement by guide members 38 to align the same while the punch member 32 may be suitably keyed to the platen 24 as at 40. Between the die member 34 and the bed plate 36, a spacer 42 is disposed. Spacer 42 is preferably of a sandwich type as shown in Fig. 2 and includes two plates of steel or other suitable strong metal 44 and 46. Between the two plates is disposed a layer of a low melting point metal 48. This may be of any of the well known low melting point alloys such as bismuth and/or cadmium alloys, for example, Woods metal, which melts at avery low melting point or it may be a market item known as Cerro Matrix. It is quite apparent also that any of the usual lead alloys that are of low melting point character may be used, however, it is pointed out here that the layer 48 should be made of as low a melting point metal as is possible since the less heat required for the subsequent destruction operation, the more facile is the use of the sandwich. The layer 48 may be bonded to the strong metal sheets, riveted thereto or merely placed therebetween.

In the operation, when the press becomes jammed due to a dead center position of the crank 28 and link 26, it is merely necessary to take -a blow torch and heat the spacer sandwich 42 until the low melting point metal layer 48 melts and flows outwardly. This gives a clearance equal to the thickness of the low melting point alloy layer so that the dead center condition is easily over-come. The low melting point metal, which has been melted during the operation, is recovered and reused in a subsequent spacer sandwich.

The thickness of the low melting point metal layer may vary in accordance with its use but I have found that in most cases a low melting point met-a1 layer of approximately one-half inch thick yields the desired results. However, it is apparent that this may vary in connection with the size of the press, type of dies being used, etc., and the specific dimensions of the spacer therefor form no part of this invention.

It is further manifest that the drawing of the press as shown in Fig. 1 is diagrammatic and that the spacer 42 may be used in connection with any type of press wherein dead centering presents a problem. In other words, the spacer may be used in conventional eccentric presses as well as crank type presses or in any other type of mechanical press wherein close setting of the die elements causes possibility of jamming of the press during its operation.

The use of the sandwich spacer 42 permits a veryrapid remedy to a usually ditficult problem since the mere heating of the spacer eliminates the difiiculty whereas in the past it was necessary to dismantle the press in order to break the dead center position. Furthermore, the use of accurately dimensioned spacers permits quick replacement without the necessity of adjustment to the press since each spacer may be held within rather close dimensional tolerances.

In place of melting the low melting point metal by means of a blow-torch or other external source of heat, it is possible to make up the sandwich so that the upper member 44 thereof is constructed as shown at 45 in Fig. 3. In this instance, a plurality of heating elements 47 are suitably maintained within the steel supporting plate, which elements may be quickly connected to a source of electric current when a dead center condition arises so that the heating of the low melting point metal layer 48 is accomplished by means within the sandwich. In place of the electrical element, many other suitable heating means may be incorporated in the steel plates, for example, tubes through which a superheating fluid may be passed or through which hot gases may be circulated, come fully within the scope of our invention. Similarly, the tubes may be in either the upper or lower plate of the sandwich.

Still another modification of the invention is shown in Fig. 4, wherein the heating elements or tubes are cast within the low melting point alloy layer 49.

It is understood that in all cases, the area of the heat destructible layer of low melting point alloy should be sufliciently large and means for supporting the die thereon properly designed so as to substantially prevent any plastic deformation under the specific loading condition in which the spacer is used. This can be easily calculated for any specific alloy in accordance with its physical characteristics as well known to those skilled in the art.

In some cases, the spacer may only be a plate of low melting metal rather than a sandwich or laminated structure, although we have found that the sandwich is more desirable in most cases since it presents a means for distributing the load more evenly. However, it is apparent that in some applications where large area dies are being used, the load distribution will be equalized without the use of additional plates.

The invention noted herein is useful in all types of presses whether used for punching, forming or coining operations as well as being useful in connection with all types of machine shop equipment wherein dead centering presents a problem.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

In combination with a crank type press having normal tendencies toward dead centering during operation thereof, wherein the press includes a punch and die element relatively movable with respect to one another and wherein the die is adapted to rest upon a portion of the press in immovable relation thereto, a spacer adapted to be disposed between the die and that portion of the press upon which the die is disposed, said spacer consisting of a sandwich including three layers wherein the centrally disposed layer is of a low melting point alloy and the other two spaced layers are steel, said spacer having an area sufficient to prevent substantial plastic deformation thereof during operation of the press under normal operating loads, the centrally disposed alloy layer of said spacer being capable of being destroyed by heat upon dead centering of the press for providing clearance to overcome the dead center condition.

References Cited in the file of this patent UNITED STATES PATENTS 995,537 Hertner et al. June 20, 1911 1,551,342 Steenstrup Aug. 25, 1925 1,847,620 Miller Mar. 1, 1932 1,882,755 Boynton Oct. 18, 1932 1,960,166 Rode et al. May 22, 1934 2,017,784 Clouse Oct. 15, 1935 FOREIGN PATENTS 611.231 Germany Apr. 2, 1935 

